A refrigerant pack is widely used for cooling at the time of storage or transportation of various fresh products, and typically, this is repeatedly used. The refrigerant pack is provided with a refrigerant substance having a cooling action, and is configured to seal this refrigerant substance in a container having thermal conductivity.
As the refrigerant substance, a refrigerant substance containing a colorant such that the presence thereof is easily visually recognized from the outside of the refrigerant pack is known, and for example, a refrigerant pack in which a refrigerant substance colored by a dye is enclosed and the enclosed amount is easily visually recognized from the outside is disclosed (refer to PTL 1).
However, in the refrigerant pack described in PTL 1, there are problems in which, even in a case where the refrigerant substance contains a dye, it is difficult to visually confirm the cooling state such as the presence/absence of freezing, and it is difficult to visually recognize whether the refrigerant pack is sufficiently cooled to the desired temperature at which cooling is possible or not, or the cooling state.